The present invention generally pertains to a backrest for a vehicle seat and, more particularly, to an adjustable backrest having an energy-absorbing recliner arrangement.
When a vehicle experiences the very rapid accelerations of decelerations of a collision, large forces are imparted to all its components. To protect the occupants of such a vehicle, energy management means are incorporated at appropriate locations throughout the vehicle. To this end, a multitude of seats have been introduced that propose to offer some measure of occupant protection during an impact. Of the various types of crash seats, the most widely accepted are those that absorb energy by plastic deformation of their components. Any deformable features, however, must be balanced with the strength requirements necessary for normal operating conditions and reliability needs. Therefore, a seat should be rigid enough for everyday use, but when an impact load on the seat becomes so great as to exceed a predetermined magnitude, energy management means within the seat should become operative. Such means should dissipate energy by offering a controlled yielding of appropriate seat components.
A vehicle seat arrangement typically comprises a cushion unit and a backrest unit wherein the backrest unit is pivotally mounted to the cushion unit. The pivoting backrest offers several fundamental features, including the ability to be adjustably reclined rearward from an upright position to accommodate occupant comfort. Any number of arrangements are available by which the reclination can be selectively controlled, but the present invention is broadly directed to a class of seats with reclining devices known as linear adjusters.
Linear adjuster are well known and include pneumatic or hydraulic springs, rods with friction clutches or teeth engagingly held, jackscrews or the like. They generally comprise adjustable elongate means having a first end usually mounted on the frame of the cushion unit or seat hardware and a second end usually mounted on the backrest at a selected distance away from the backrest pivot axis. They are further characterized as those arrangements that can accommodate an increase or decrease of the distance between the two selected mounting points that result when the second mounting location rotates with the backrest unit. The adjuster is normally locked to prevent undesired movement of the backrest, but when the adjuster is released, the backrest can be pivoted to a desired position and the adjuster can then again be relocked. During rotation, the adjuster means accommodates the resulting change in the distance between the adjuster's two mounting locations.
The present invention is novel in that it comprises a dedicated energy management device incorporated into a linear adjuster arrangement. The arrangement, unlike most other seat backrest energy management means, is such that it is effective in both front and rear impact modes. In the preferred embodiment, a pneumatic strut has a first end pivotally secured to the seat cushion frame or seat hardware. An energy-absorbing corrugated tube cooperatively couples a second end of the strut and the seat backrest at the second mounting location. During normal operation, the tube acts as a stable extension of the strut, thereby accommodating rotation of the backrest about the pivot axis. However, when forward or rearward impact forces exceed a predetermined magnitude, the tube will stretch or compress accordingly, thereby absorbing energy.
Other seats have shown energy management means for a seat backrest, but each has disadvantages as noted below. For example, the seat in U.S. Pat. No. 3,501,200 presents a deformable support bracket but is applicable only for a fixed backrest. U.S. Pat. No. 3,832,033 has dedicated energy management means that are only applicable for frontal impacts, the means comprising an elastomeric block that stores backrest energy but later returns most of that energy to the backrest upon rebound. The seat shown in U.S. Pat. No. 3,953,068 uses rotational energy management devices that are not applicable for a reclinable seat. Finally, FIG. 6 shown in U.S. Pat. No. 3,734,562 teaches of an energy management system designed only for forward impacts, and that is not applicable for a reclinable seat.